SPECIES H YBR1 DlZA TlON 



239 



characters, however, it crosses freely with members of the tabacum 

 group, and yields reciprocal hybrids which are equivalent throughout. 

 In Fig. 103 on the right is illustrated a plant of N. tabacum angustifolia 

 and beside it the F l hybrid with N. sylvestris. The figure shows clearly 

 how faithfully the characters of the N. tabacum parent are reproduced in 

 the hybrid. The leaves are long, narrow and petioled, the upper ones 

 strap-like and pendant, the flowers are narrow and have narrow, sharply 



FIQ. 102. Typical plant of Nicotiana sylvestris. 



pointed lobes these and the general habit of growth are all characters 

 clearly referable to the N. tabacum parent. A very different variety of 

 tabacum, such as the variety known in the University of California Bot- 

 anical Garden cultures as N. tabacum " Cuba" gives corresponding results. 

 This variety is tall and bears white flowers many of which are quadrimer- 

 ous instead of pentamerous as is normally the case in Nicotiana. These 

 characters are faithfully reproduced in the hybrid with sylvestris as is 

 shown in Fig. 104. N. tabacum "Cuba" is peculiar among the tabacum 

 varieties in its ability to develop seed capsules in the absence of fertiliza- 

 tion, and these may sometimes contain a few viable seeds. This is appa- 



